Corrugated fiberboard containers are used in many high humidity bulk packaging applications such as for fresh fruit and produce items. To overcome the known impairment in the strength of corrugated fiberboard in high humidity service, it is customary to treat such containers, or the corrugated fiberboard sheets or blanks from which the containers are formed, by impregnating them with a material resistant to moisture.
Applications can also include films for food items such as cookie and cracker packaging. In these particular cases, the object of the package is not only to hold the contents, but also to provide resistance to moisture vapor transmission (from the environment to inside the package). Otherwise, moisture vapor would diminish the shelf life of the contained cookies, crackers, or the like. Shelf life is determined by the time it takes the products to pick up sufficient moisture to render them stale. In cookie and cracker packaging applications, for example, the general object of the barrier layer is to substantially keep moisture out or to slow its ingress.
In the past, external coating layers of high density polyethylenes (HDPE) were needed to achieve a target water vapor transmission resistance (WVTR) or aqueous fluid (hot or cold) transmission resistance. Typically, these external coatings also included the addition of a second coating layer to provide other desired properties such as tear resistance, and/or mechanical properties such as heat seal. Often the materials used in the second coating layer were relatively poor in WVTR or aqueous fluid (hot or cold) transmission resistance.
Such combinations typically result in added costs and may affect other important properties necessary to the packaging industry. Therefore, a need exists for a moisture barrier film or container fabricated such that the article will have relatively good WVTR or aqueous fluid (hot or cold) transmission resistance combined with improved physical properties.